The current proposal is aimed at an in-depth study of the clinical significance of immune complexes in serum samples of patients with various forms of leukemia. Serum samples will be analysed using several extremely sensitive assay, including the solid phase Clq SPA binding technique as well as the Raji solid phase anti-C3 techniques. Correlations between the presence of positive tests for circulating immune complexes and clinical or disease status will be made. In addition, samples strongly positive for immune complexes will be analyzed with particular attention to attempts to identify leukemia-specific or immune complex preparations. It is hoped that direct definition of such antigens in leukemic sera may provide direct insight into possible control mechanisms important in the specific disease state.